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EP-4741750-A1 - DIMPLE TUBULAR HEAT EXCHANGER USED FOR APU

EP4741750A1EP 4741750 A1EP4741750 A1EP 4741750A1EP-4741750-A1

Abstract

A heat exchanger includes a microtube defining a lumen and including a plurality of dimples configured to cause a turbulent flow of a fluid within the lumen of the microtube. The microtube has an outer diameter equal to or less than 5 mm.

Inventors

  • ZHOU, Ding-wei
  • DO, QUANG

Assignees

  • Honeywell International Inc.

Dates

Publication Date
20260513
Application Date
20251022

Claims (15)

  1. A heat exchanger comprising: a microtube defining a lumen and including a plurality of dimples configured to cause a turbulent flow of a fluid within the lumen of the microtube, wherein the microtube has an outer diameter equal to or less than 5 millimeters (mm).
  2. The heat exchanger of claim 1, wherein the fluid within the lumen of the microtube is a first fluid comprising an oil, wherein the heat exchanger is configured to allow a second fluid to flow in contact with an external surface of the microtube.
  3. The heat exchanger of claim 2, wherein the second fluid is air.
  4. The heat exchanger of any of claims 1-3, wherein the microtube comprises a tube wall defining the lumen, the tube wall comprising an inner surface and an outer surface external to the lumen, wherein each dimple of the plurality of dimples comprises a height variation of the inner surface of the microtube.
  5. The heat exchanger of claim 4, wherein the height variation comprises a dimple depth of equal to or greater than five per cent (5%) of the outer diameter of the microtube.
  6. The heat exchanger of claim 5, wherein the dimple depth is equal to or less than 15% of the outer diameter of the microtube.
  7. The heat exchanger of any of claims 1-6, wherein the microtube comprises a tube wall defining the lumen, the tube wall comprising an inner surface and an outer surface external to the lumen, wherein each dimple of the plurality of dimples comprises a height variation of the outer surface of the microtube.
  8. The heat exchanger of any of claims 1-7, further comprising a plurality of microtubes configured to have a spacing between respective outer surfaces of adjacent microtubes of 3 mm or less.
  9. The heat exchanger of any of claims 1-8, wherein the plurality of dimples are uniformly distributed along a length of the microtube.
  10. The heat exchanger of claim 9, wherein: the plurality of dimples includes a first dimple, a second dimple, and a third dimple, the first dimple is displaced from the second dimple by a first axial distance, the second dimple is displaced from the third dimple by a second axial distance, and the first axial distance is equal to the second axial distance.
  11. The heat exchanger of any of claims 1-10, wherein the plurality of dimples are uniformly distributed about a circumference of the microtube.
  12. The heat exchanger of claim 11, wherein: the microtube defines a substantially circular outer perimeter, the plurality of dimples includes a first dimple, a second dimple, and a third dimple, the first dimple is displaced from the second dimple by a first angle, the second dimple is displaced from the third dimple by a second angle, and the first angle is equal to the second angle.
  13. The heat exchanger of any of claims 4-12, wherein the plurality of dimples are configured to increase mixing of the fluid flowing with the lumen by disturbing a boundary layer of the fluid relatively near the tube wall.
  14. The heat exchanger of claim 13, wherein the increased mixing of the fluid is configured to increase a rate of transfer of thermal energy from the fluid.
  15. A method of making a microtube, the method comprising: printing a microtube defining a lumen, the microtube comprising an inner surface and an outer surface; and printing a plurality of dimples in the inner surface of the microtube, each dimple of the plurality of dimples being configured to cause a turbulent flow of a fluid within the lumen of the microtube, and wherein an outer diameter of the microtube is equal to or less than 5 millimeters (mm).

Description

This application claims the benefit of U.S. Provisional Patent Application No. 63/717,652, filed 7 November 2024, the entire contents of which is incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to heat exchangers. BACKGROUND A heat exchanger may be positioned within fluid streams of a fluid handling system, or in the exhaust gases of a process, in order to transfer heat between the fluids and/or gases. The efficiency of a heat exchanger depends at least in part on the heat transfer coefficients between the fluids and/or gases. SUMMARY In some examples, this disclosure describes a heat exchanger comprising: a microtube defining a lumen and including a plurality of dimples configured to cause a turbulent flow of a fluid within the lumen of the microtube, wherein the microtube has an outer diameter equal to or less than 5 millimeters (mm). In some examples, this disclosure describes a method of making a microtube, the method comprising: printing a microtube defining a lumen, the microtube comprising an inner surface and an outer surface; and printing a plurality of dimples in the inner surface of the microtube, each dimple of the plurality of dimples being configured to cause a turbulent flow of a fluid within the lumen of the microtube, and wherein an outer diameter of the microtube is equal to or less than 5 millimeters (mm). The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. FIG. 1 is a perspective view illustrating an example heat exchanger, in accordance with examples of the present disclosure.FIG. 2 is a cross-sectional side view of an example dimpled tube for use with a heat exchanger, in accordance with examples of the present disclosure.FIG. 3 is a cross-sectional side view of an example dimpled tube for use with a heat exchanger, in accordance with examples of the present disclosure.FIG. 4 is a cross-sectional side view of an example dimpled tube for use with a heat exchanger, in accordance with examples of the present disclosure.FIG. 5 is a cross-sectional longitudinal view of an example dimpled tube for use with a heat exchanger, in accordance with examples of the present disclosure.FIG. 6 is a cross-sectional side view of an example non-dimpled microtube with a first fluid flowing through the non-dimpled microtube and a second fluid surrounding the tube.FIG. 7 is a cross-sectional side view of an example dimpled microtube with a first fluid flowing through the dimpled microtube and a second fluid surrounding the microtube, in examples with examples of the present disclosure.FIG. 8 is a cross-sectional side view of an example dimpled microtube for use with a heat exchanger, in accordance with examples of the present disclosure.FIG. 9 is a flowchart of an example method of exchanging heat via heat exchanger, in accordance with examples of the present disclosure. DETAILED DESCRIPTION This disclosure relates to a heat exchanger including one or more dimpled tubes. In some examples, the heat exchanger includes a plurality of dimpled tubes, and the tubes may be microtubes, e.g., each tube having an outer diameter that is equal to or less than about 5 millimeters (mm), or equal to or less than about 3 mm. In some examples, the heat exchanger is configured to transfer heat from a first fluid (e.g., cool the first fluid) to a second fluid. The first and second fluids may each be a liquid, a gas, an oil, a vapor, and/or a liquid/gas mixture. In some examples, the first fluid may be a gas, and the second fluid may be air. In accordance with aspects of this disclosure, a heat exchanger includes dimpled microtubes configured to increase turbulent flow of a liquid within the tube. The turbulent flow may increase the heat transfer coefficient between the fluid within the tube and a fluid external to the tube with a decreased pressure drop penalty. For example, the turbulent flow may disturb or break up a boundary layer of the fluid relatively near the tube wall and away from the central portion of the tube. The turbulent flow may also increase mixing of the fluid within the tube, e.g., cause fluid near the tube wall to mix with fluid near the central portion of the tube. Disturbing and/or breaking up the boundary layer and mixing of the fluid within the tube may increase the heat flux transferred between the fluid internal to the tube and the fluid external to the tube, e.g., through the tube wall. For example, the temperature difference may be greater between the two fluids because of the breaking up of the boundary layer and mixing of the fluid within the tube, e.g